Spacer expander and process therefor

ABSTRACT

A spacer expander is of U shape in radial cross section and has upper and lower pressure supporting surfaces which have projections for urging side rails radially. Intermediate curved portions extend between adjacent pairs of upper and pairs of lower pressure supporting surfaces for circumferentially connecting the same.

United States Patent 1191 Miyamoto July 17, 1973 [5 SPACER EXPANDER AND PROCESS 277/140, 141, 139, 160, 149, 202

THEREFOR [75] lnventor: Mikio Miyamoto, Omiya, Japan [56] References cued v UNITED STATES PATENTS [73] Assgnee Rmg 3,633,260 1/1972 warrlck 29/l56.6 Japan 2,907,101 10/1959 Hamm i 29/l56.6 22 Filed: Aug. 5 1971 3,355,180 ll/l967 Hamm v i 267/15 PP N05 169,447 Primary Examiner-Charles W. Lanham Related Applicafion Data Assistant ExaminerD. C. Crane [62] Division of $61. No. 54,279, July 13, 1970, Pat. No. Anamey sughwe Rothwen Macpcak 3663930 571 ABSTRACT [30] Foreign Application priority Data A spacer expander is of U shape in radial cross section 1 2 9 44 4 3 and has Pressure supporting Surfaces Ju y l Japan ,5 8 l which have projections for urging side rails radially. In- [52] U S. CL 29/1566 29/156 63 termediate curved portions extend between adjacent [51] in C1. J."'33:::Jjjjjji'ijjiii'jj: imp 15116 pppp pf upper and ppipp pf lpwpp ppppppppg [58 Field of S earcli 29/156 6 156.61 Surfaces circumferentiauy cnnecting the Same- 1 Claim, 5 Drawing Figures PATENTEU JUL 1 1197s FIG.3'

FIG. 5

SPACER EXPANDER AND PROCESS THEREFOR This is a division of application Ser. No. 54,279, filed July 13, 1970, now US. Pat. No. 3,663,030.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION SUMMARY OF THE INVENTION The present invention provides a spacer expander which is U shape in radial cross section, formed of Steel sheet which has a high strength and a resiliency in circumferential, radial and axial directions so as to overcome the problem of the decrease of the strength due to fatigue allowing long usage with uniform pressure and resiliency.

It is another object of this invention to provide a pro cess for manufacturing a spacer expander of U shape in radial cross section which is less expensive and forms a simple structure.

According to one aspect of the present invention, there is provided a spacer expander of U shape in radial cross section which comprises upper and lower pressure supporting surfaces which have projections for urging side rails radially. Outer vertical peripheral surfaces connect axially aligned upper and lower pressure supporting surfaces and connect pairs of adjacent upper pressure supporting surfaces and are U shape in axial cross section and alternately, other intermediate curved portions connect circumferentially, adjacent pairs of lower pressure supporting surfaces, which are also U shaped in axial cross section. The respective intermediate curved portions are preferably of the same circumferential and radial width.

Other objects, features and advantages of the present BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of part of the original stamped metal sheet forming the spacer expander of this invention.

FIG. 2 is a front view of a portion of the original sheet curved in U shape in radial cross section.

FIG. 3 is a front view of a portion of the spacer expander formed from the sheet shown-in FIG. 2, according to this invention.

FIG. 4 is a perspective view of the expander portion shown in FIG. 3.

FIG. 5 is a longitudinal side sectional view of part of the expander inserted into a piston groove with side rails in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is now made to the drawing, and particularly to FIG. 1. In the process of forming the spacer expander of this invention, a steel sheet strip is cut to define shallow cutouts a of rectangular form and is also cut to define deep cutouts b of rectangular form on the opposite side of the shallow cutout a. Cutouts b have the same width as the shallow cutouts a in symmetry. The sheet strip is also cut with a deep cutout b in rectappropriate for the circular expansion and contraction angular form adjacent to each shallow cutout a and is also cut in shallow cutout a in rectangular form on the opposite side to the deep cutout b and of the same width as that of the deep cutout b in symmetry, as shown in FIG. 1, and so on, in turn in the same distance and adjacent to each other. Thus, there are provided projections, upper and lower pressure supporting surfaces, and vertical surfaces between the cutouts a and b designated by A, and there are also provided upper intermediate portions B connecting the adjacent upper pressure supporting surfaces and traverse plates A are also provided as are lower intermediate portions 8' for connecting between the adjacent lower pressure supporting surfaces and traverse plates A.

The original cut plate is then bent along the bottom edge, lines of the shallow cutout a in such a manner that the projected portions of the traverse plate A are directed perpendicularly to the plane of the figure so as to form upper and lower projections l and l as shown in FIG. 2. Then, the original plate is also bent along the bottom edge lines of the deep cutout b in such a manner that the upper and lower portions of the transverse plate A become perpendicular to the plane of the figure on the back thereof so as to form upper and lower pressure supporting surfaces 2 and 2' andupper and lower intermediate connecting portions B and B which connect the upper pressure supporting surfaces and the lower pressure supporting surfaces, respectively in pairs and vertical surfaces 3 which give U shape in radial cross section forming a channel type spacer expander.

Thereafter, the intermediate connecting portions B and B are bent and project in such a manner that the upper portion projects downwardly while the lower portion projects upwardly as shown in FIG. 3 in U shape. Then, the bent plate is circularly bent so that the projections l and l' are disposed on the inside of the circular shape as shown in FIG. 4, so that the opening side of the U shape is disposed inside.

Finally, the spacer expander thus formed is combined with side rails S in such a manner that the side rails S are disposed on the upper and lower pressure supporting surfaces 2 and 2' and within a piston groove G as shown in FIG. 5 so that the opening portion of the U shape faces on the bottom of the piston groove to define a piston ring of the channel type. In FIG. 5, reference character 0 designates an oil groove in a piston groove and C denotes a cylinder.

It should be understood from the foregoing description that since the spacer expander of this invention comprises upper and lower intermediate connecting portions for connecting alternate pairs of upper pres sure supporting surfaces and lower pressure supporting surfaces, respectively, and are bent in U shape, the spacer has high strength as a whole and high resiliency of the spacer expander upon disposition thereof within a piston groove. Particularly, it is noted that since the radial widths of the upper and lower pressure supporting surfaces 2 and 2' and intermediate portions B and B are the same, the effect is one of high strength and, particularly a decrease in the fatigue thereof for repeated stresses.

It should be understood also that since the spacer expander of this invention has strong resiliency in the circular or circumferential radial and axial directions thereof and has high strength, it always provides uniform pressure for long periods so that it acts superior in combination with side rails as a piston ring in a piston groove.

It should be also understood that the spacer expander may be manufactured simply and less expensively.

What is claimed is:

l. A process of forming a spacer expander for circular disposition within a piston groove and for urging side rails disposed on each side thereof radially outwardly of said groove, said method comprising the steps of:

forming alternate, shallow and deep cutouts on opposed sides of a sheet metal strip, at spaced longitudinal positions, which define transverse plate portions longitudinally joined by longitudinally extending intermediate portions, and ending portions of said transverse plate along the bottom edge lines of said shallow cutout in such a manner that the projecting portions of said transverse plate portions extend perpendicular to the plane of the sheet and outwardly thereof, bending other portions of said transverse plate portions along the bottom edge lines of said deep cutouts to define upper and lower surface pressure supporting surfaces which are perpendicular to the plane of said sheet and extending perpendicularly to said projections, and bending said intermediate portions between alternate pairs of said transverse plates such that said intermediate portions which join upper pressure supporting surfaces project downwardly while intermediate por' tions joining lower pressure supporting surfaces project upwardly and curving the same into U shaped axial cross sectional configuration and bending the spacer expander as a unit in a circle such that the open side of the U shaped spacer expander faces internally within the piston groove receiving the same.

# I i t 

1. A process of forming a spacer expander for circular disposition within a piston groove and for urging side rails disposed on each side thereof radially outwardly of said groove, said mEthod comprising the steps of: forming alternate, shallow and deep cutouts on opposed sides of a sheet metal strip, at spaced longitudinal positions, which define transverse plate portions longitudinally joined by longitudinally extending intermediate portions, and ending portions of said transverse plate along the bottom edge lines of said shallow cutout in such a manner that the projecting portions of said transverse plate portions extend perpendicular to the plane of the sheet and outwardly thereof, bending other portions of said transverse plate portions along the bottom edge lines of said deep cutouts to define upper and lower surface pressure supporting surfaces which are perpendicular to the plane of said sheet and extending perpendicularly to said projections, and bending said intermediate portions between alternate pairs of said transverse plates such that said intermediate portions which join upper pressure supporting surfaces project downwardly while intermediate portions joining lower pressure supporting surfaces project upwardly and curving the same into U shaped axial cross sectional configuration and bending the spacer expander as a unit in a circle such that the open side of the U shaped spacer expander faces internally within the piston groove receiving the same. 